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Патент USA US2407460

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-Sept.1o,v194e.
f
B. VAN RYN
»
2,407,460
SWITCH FOR HIGH FREQUENCY CIRCUITS
Fílèd Hay 15, 1943
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2,407,460
Patented Sept. 10, 1946l
UNITED’STATES PATENT OFFICE
2,407,460
SWITCH FOR HIGH-FREQUENCY CIRCUITS
Bernard van Ryn, Chelmsford, England, assign
or to Radio Corporation of America, a corpora
tion of Delaware
Application May 15, 1943, Serial No. 487,426
In Great Britain April 2, 1942
4 Claims.
v
(Cl. 179-1715)
2
1
impedance to radio-frequency energy, a source
of direct current energy, and a switch for con
rangements for electric circuits carrying radio
necting said source to the anode (or element serv
frequency energy and particularly for radio-fre
ing as anode) of said rectifier in such sense as to
quency oscillators.
.
~
It is frequently required that a circuit carrying Ul cause said rectifier to become conducting so' as to
present a low impedance vto radio-frequency
radio-frequency energy, such as an oscillator
'I‘he present invention relates to switching ar
valve having a radio-frequency output, shall be
Y
energy.
If desired, there may be connected between
screened so that it shall not cause interference
with other apparatus, and yet that access shall be
available to the circuit for the purpose of switch
said anode and said switch, a. radio-frequency fil- l
ter comprising a series-connected resistor or in
ing it out of operation.
`
As a case inpoint, mention may be made of a
Fig. 1 of the accompanying drawing illustrates
ductor and a shunt-connected condenser.`
a particular exemplary circuit arrangement for a
superheterodyne receiver in which a beat fre
telephone and continuous wave (C. W.) telegraph
reception in which it; is important that as few 15 quency oscillator is employed for continuous wave
(telegraph) reception; vand
valves shall be used as conveniently possible and
superheterodyne radio receiver designed for bo-th
FigfZ shows arcircuit diagram of an alternative
in which, to this end, the first audio-frequency
. amplifier stage and the beat frequency oscillator
embodiment.
vention to such a case.
'
quency from reaching, by external coupling, earl
.
~
valve, which may be a triode, has its cathode con
nected to >ground through a condenser-shunted
In a case such as that outlined above, in o-rder `
to prevent any of the harmonics of the beat fre-v
..
Referring to Fig. 1, a common valve V is used
to function as the- first audio-frequency amplifier
(A. F. amp.) and as the beat-frequency oscilla.
tion generator (B. F. O.) ofthe receiver.` The
share in common a single valve. It is to be under
stood that a case of this nature is to beregarded
merely as exemplary and not as limiting the in
25 bias resistor BR and its anode connected to the
control grid -througha variable condenser C2, inv
ier stages of the receiver, .it is usual to mount the
series with a further condenser C3, which may or
may not be variable, and a parallel-tuned circuit
v Valve serving the two purposes mentioned in a
separate screening box.
-
TC.y The anode fof the Valve'ís also connected,
For the reception of modulated waves (tele
phone reception), however, it is required to switch 30 through a radio-frequency choke HFC in series
with an audio-frequency choke LFC to the posi
off the beat vfrequency oscillator without, in any
tive terminal HT-i- ofthe usual source of high
Way, interfering with the performance of the
potential energy (not shown), the negative ter
valve insofar as its audio-frequency amplifying
functions are concerned. Such a switching oper
mina-l of which is,.as is usual, grounded or other
ation would present no problem were it possible '
wise connected to the cathode of the valve. `
,
Audio frequency input is applied fromthe out
or permissible, as frequently it is not, to mount
the necessary switching apparatus within the box
which contains the valve and the immediately
put of the second detector, represented by block
D, to some convenient point on the inductor L of
associated complementary instrumentalities andv ' the vparallel-tuned circuit TC through a radio fre
quency choke HFC?` between the grid end of which
elements. The diñîculty presented, when such
mounting within the box is not possible or per
missible, could of course be overcome by mount
ing the switch outside the box and bringing a lead
from the inside of the box tothe switch. Since,
however, such a lead would be carrying radio 45
frequency energy, it and the switch to'which'it vis
to be connected would have to be screened, 'a con
dition which, under certain circumstances, >as
when the switch is' required to perfo-rm other
functions, presents its own problems.
According to the invention, a switching ar
rangementfor 'a circuit, vor circuit element, carry
ing radio-frequency energy includes,'co-nnected„
and ground there is connected a radio frequency
bypass condenser RFC. Audio frequency output
may be taken from a lpoint between the two
chokes HFCand LFC and fed through a block
ing condenser BC to the final audio stage, repre
n sented by block O.
Thefswitching device'according to the inven
tionis connected to a point X between the series
connected variable condenser C2 and the con
denser C3, and comprises a rectifier W connected
between this point and gro-und, a resistor'R con
nected betweenfthis. same point (that is, effec
tively, between one'terminal ofthe'rectiñer) and
one terminal of a make-,break switch S, the'other
across the circuit or circuit element, a rectifierl
which in its normal condition presents a .highA 55 terminal of >which is connected tothe -positive ter
2,407,4ec
3
4
minal HT+ of a source of energy, and a decou
LFC, to the positive terminal HT+ of the usual
pling condenser Cl connected between the said
source of high-tension energy (not shown), the
negative terminal of which is, as is usual, ground
one terminal of the switch and ground.
The rectiñer W is so connected that when the
ed or otherwise connected to the cathode of the
switch is closed to condition the tube as the beat
valve.
frequency oscillator for C. W. reception the posi
Audio-frequency input is derived from a point
tive terminal l-IT-l- of the source of energy, which
source may be the same as that connected to the
anode of the valve V, is connected to that termi-l
on the low-frequency volume control resistor LR
and applied over lead AI to some convenient point
Y on the inductor L of the parallel-tuned circuit
nal of the rectifier which is connected to the
junction point X of the series connected condens
ers. The rectifier therefore will be> conductive l ,
and will provide a path of low impedance between 1,
the said point and ground.
By way of further explanation or" the operation
of the system disclosed in Fig. 1, tube V operates, '
for the reception of radio telephony (voice), onlyas an audio frequency amplifier, and for the re
Y
TC, and audio-frequency output may be taken
from a point between the two chokes HFC and
LFC and fed through a blocking condenser BC to
the final audio stage, represented by block O‘.
The switching device according to the inven
tion is connected to a point X between the series
connected variable condenser C2 and further
condenser C3, and comprises diode portion DI of
the double-diode-triode valve V connected be
ception of radio telegraphy (code) it operates as> "
tween this point and ground, a resistor R oon
a combined audio frequency amplifier and beat -
nected between this same point (that ineffective
ly, between one terminal of the rectifier) and one
terminal of a make-break switch S, the other ter
minal of which is connected to the positive termi
frequency' oscillator.
In the latter instance;
switch S will be closed and tube V will function as
a Hartley oscillator by reason of the connection
of the grid to one side of the frequency determin
nal I-lT-i- of a source of energy, and a decoupling
ing circuit TC, the connection of the anode
condenser Ci connected between the said one ter
through closed switch S, resistance R and con- V
minal of the switch and ground.
,
y
denser C3 to the other side of circuit TC, and the
The diode portion DI is so connected, that
connection of the cathode through condenser
when the switch S is closed, the positive» terminal
RFC to an intermediate point on the coil L of
HT+ of the source of energy, which source may
be the same as that connected tothe anode> of
the valve V, is connected to the anode of the di
ode, the diode is conductive and provides a path
circuit TC.
'
‘
Audio frequency signals from the seco-nd detecH
tor D are also applied to the grid of tube V by
way of the tapped connection on circuit TC which
for audio frequency is connected to ground
through condenser C3 and the rectifier W which
it will be remembered provides a path of low
impedance in the closed position of switch S.
The heterodyne beat resulting from 'the interac
tion in tube V of the audio frequency signals and
of low impedance between the point X and
ground. The other diode D2 serves as a detector
and also supplies anv AVC bias voltage Vto the lead
AVC.
'
The resistive value of the `resistor R may be
quite high (for example 2 megohms) and'it and
the decoupling condenser CI then constitute a
the output of the tube and be amplified and in
satisfactory radio-frequency filter so that the
lead beyond this filter, and the switch, will be at
dicated in the usual manner.
substantially zero radio-frequency potential.
the locally produced oscillations will appear in .
As heretofore ex
plained the radio frequency filter constituted by
R and Cl prevents thefoscillations of the beat
frequency oscillator from being transmitted to
earlier stages of the receiver through the switch
Sand its connections.
'
'
i
' For the reception of radio telephony, the open
ing of switch S removes the voltage from across
rectifier W which therefore acts as a high imped
ance device, and being shunted effectively across
the space discharge path of the tube prevents the
tube from oscillating. The tube and associated
circuit elements (TC, BR, LFC and BC) will how
l. A circuit arrangement comprising a tube
provided at least with a cathode, control grid and
anode, two condensers and a tuned circuit con
nected in series and in the order named between
said anode and control grid, the cathode being
connected to ground, means for coupling a source
of audio frequencies to said tuned circuit, a recti
ñer so connected betweeen the- junction point of
said oondensers and ground as to present a high
impedance to radio frequency energy and to
thereby condition the tube to ,function as an audio
ever function as an audio frequency ampliñer.
The rectifier may be a dry-plate rectifier, as
illustra-ted in Fig. 1, or a diode, or a triode acting
as such, or it may be the diode-portion of a di
ode-triode, or, as illustrated in Fig. 2 of the ac
- frequency ampliiienand a switch for connecting
companying drawing, one of the diode-portions
of a double-diode-triode, the other diode-por
tion in this circuit serving for detection and for
the production of ‘an automatic volume-control
bias.
Referring to Fig. 2, the triode part of the valve
2. A circuit arrangement as claimed in claim 1
wherein 'there is connectedacross said rectifier
a resistor and condenser in series, said switch be
ing connected on one side to the junction of said
resistor 'and condenser and on~ the other side to
V serves as a beat-frequency oscillato-r and audio
frequency amplifier. The cathode of the valve is
connected to earth through a condenser-shunted
bias resistor BR and the anode is connected to
the-control grid of the valve through a variable
condenser C2, in series with a further condenser
C3, which >may or may not be variable, and a par
allel-tuned circuit TC. The anode of the valve is
a potential across said rectifier to reduce theim.
pedance of said rectiñer for radio frequency and,
to thereby condition the tube to function as an
oscillation generator.
f the positive terminal of a source of current, said
resistor and condenser' constituting a radio fre
quency filter to prevent radio frequency being
transmitted to said switch and its connections. Y
3. A circuit arrangement as claimed in Vclaim 1
wherein said rectifier is a diode. ,
4. A circuit arrangement as claimed in claim l
wherein said tube is a diode-triode'and the recti
iier constitutes the` diode portion of the tube.
also connected, through a radio-frequency‘choke
HFC in series with an audio-frequency choke
BERNARD VAN RYN.
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